The present study is a randomized double masked clinical trial consisting of two parts. The first part is a safety study utilizing patients with cystinosis who have been on bilateral treatment successfully. They now have one eye randomzied to the old cysteamine preparation and the other eye to the NDA formulation. Sample size is thirty patients of which 13 patients have been enrolled as of June 4, 1999. Ten of these patients have completed the full six months. Seven additional patients have been enrolled. The second part is an efficacy study enrolling patients who have never received treatment for their corneal cystine crystals. The eyes are randomly assigned to cysteamine eye drops in one eye and the NDA formulation in the other eye. Sample size is 15 patients followed every three months for one year. This was amended to have follow up for at least 3 months on medication but the study will follow all patients for the one year period. Nine patients were enrolled as of June 4, 1999. However by July 1, 14 patients were enrolled in the efficacy study, five from NEI, 5 from Michigan and 4 from San Diego. Since one patient dropped out before the three month evaluation, an additional two patients are to be recruited to complete the number needed. Both patients will probably come from San Diego. Details of the patient activity with respect to withdrawals from treatment and availability of follow up for the three centers are provided in the EMMES report pages cys-1 and cys-2. - cystinosis, cysteamine, corneal crystals - Human Subjects